JP3023230B2 - Two-stroke engine for outboard motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-stroke engine for an outboard motor provided with a scavenging pump, and more particularly to an arrangement of a scavenging pump suitable for an outboard motor.

[0002]

2. Description of the Related Art As a two-stroke engine, a so-called crankcase pre-compression two-stroke engine has been widely put into practical use. This engine compresses fresh air by utilizing a compression process of a crankcase and compresses the fresh air. The fresh air is scavenged into a combustion chamber through a scavenging passage or a scavenging port opened to a cylinder.

The applicant of the present invention has proposed a so-called supercharge type two-cycle engine in an earlier application (Japanese Patent Application No. 3-116595) instead of the scavenging method.
In this engine, fresh air is not compressed in a crankcase, but is forcibly compressed by a supercharger (scavenging pump) driven by the engine, and the compressed fresh air is scavenged in a combustion chamber.

[0004]

However, when this type of engine is applied to an outboard motor, various restrictions can be considered due to the limited space. First,
In order to simplify the drive mechanism provided between the crankshaft and the scavenging pump, it is necessary to move the scavenging pump as close to the crankshaft as possible. Second, if the scavenging pump is located close to the crankshaft to satisfy the first requirement,
The discharge amount to the side and upward must be minimized.

The present invention has been made in view of such circumstances, and an object thereof is to provide a rational and compact arrangement of a scavenging pump in an outboard motor.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention has a crankshaft arranged substantially vertically, and a cylinder in which a piston connected to the crankshaft reciprocates moves in a traveling direction. On the other hand, while being arranged rearward, it is driven by a crankshaft and formed on the cylinder.
In the outboard motor for e emissions <br/> gin equipped with a supercharger to supply fresh air to the combustion chamber has the supercharger side by side above the front portion of the crank shaft is disposed, to the upper and the input shaft It is protruded, the class
Link to the upper end of the shaft and communicate with the combustion chamber.
Of the fresh air supply passage inside the turbocharger to the side of the crankshaft
It is arranged to face .

[0007]

Since the scavenging pump is arranged on the crankshaft, the scavenging pump can be arranged close to the crankshaft.
Further, since the scavenging pump is disposed substantially in front of the crankshaft in the traveling direction, there is little upward projection and the engine height does not increase. In addition, the protrusion of the crankshaft to the side is reduced, and the engine width is reduced.

[0008]

FIG. 1 is a side view of an entire outboard motor to which the present invention is applied. FIG. 2 is a plan view of FIG. FIG. 3 is a side view of the engine alone. FIG. 4 is a sectional view taken along line IV-IV of FIG. FIG. 5 is a cross-sectional view taken along line VV of FIG. 2 and illustrates a drive mechanism of the scavenging pump and a height adjusting structure of the pulley. FIG. 6 is a cross-sectional view corresponding to FIG. 5, showing another structure for adjusting the height of the pulley. FIG. 7 is a cross-sectional view corresponding to FIG. 5 and is a view showing another height adjusting structure of the pulley.

In FIG. 1, an outboard motor 1 can be steered to a clamp bracket 3 fixed to a stern plate 2, a swivel bracket 4 supported on a tilt bracket 5 around a tilt pin 5, and a swivel bracket 4. A propulsion unit 6 is supported by the engine unit 7. An engine 7 mounted on the upper part of the propulsion unit 6 drives a propeller 8 by the output of the engine 7 to generate a propulsion force. Engine 7
Is surrounded by a cowling 9.

The engine 7 is a three-cylinder in-cylinder injection two-cycle engine as shown in FIG. Reference numeral 10 denotes a crankshaft arranged substantially vertically, and the crankshaft 10 includes a cylinder body 12 and a crankcase 1.
4 is disposed in a crank chamber 16 formed by the same. The cylinder body 12 is disposed substantially rearward from the crankshaft 10 in the traveling direction. A cylinder sleeve 18 is pressed into the inner peripheral surface of the cylinder body 12,
A cylinder bore 20 is formed on the inner peripheral surface of the cylinder sleeve 18.
Is formed. A piston 22 slides up and down (in FIG. 4) in the cylinder bore 20, and this movement is
4 to the crankshaft 10. A cylinder head 26 is fastened and fixed to the cylinder body 12,
A combustion chamber 28 is defined by the cylinder head 26, the cylinder bore 20, and the piston 22, and the combustion chamber 28
A spark plug 30 and an injector 32 for injecting air and metered fuel are exposed.

Reference numeral 34 denotes a scavenging pump, which is arranged substantially in front of the crankshaft 19 and side by side with the crankshaft 19. This scavenging pump 34 is fixed to the crankcase 14 by bolts 54, 54 via a mating surface 53. This scavenging pump 34 is called a so-called supercharger (supercharger), and is mechanically driven by a crankshaft 10 via a V-shaped belt 52. In addition, this scavenging pump 34
Is a roots pump type blower. When two rotors 35, 35 contacting each other are driven to rotate, the air introduced through the throttle valve 36 allows the air introduced through the throttle valve 36 to form a fresh air supply passage 37 on the discharge side. 38.

Next, a drive mechanism from the crankshaft 10 to the scavenging pump 34 will be described with reference to FIG.

A flywheel magneto 11 is fixed to the crankshaft 10 at the upper end of the crankshaft 10 by a nut 13. An output pulley 72 is press-fitted and fixed to the outer diameter of the flywheel magneto 11. On the other hand, an input pulley 62 is fixed to an input shaft 56 of the scavenging pump 34 via a flange 64 by a nut 58 and a bolt 66. A shim 68 is inserted between the upper surface of the flange 64 and the lower surface of the input pulley 62. By variously changing the thickness of the shim 68, the installation height of the input pulley 62 is changed, and the input pulley 6
2 can be adjusted to the height of the output pulley 72.

The driving force of the crankshaft 10 is transmitted to the input shaft 56 of the scavenging pump 34 via the flywheel magneto 11, the output pulley 72, the belt 52, the input pulley 62, the bolt 66 and the flange 64.

Next, the fresh air route will be described with reference to FIG.

A fresh air charging chamber 40 is connected to the downstream end of the intake passage 38 as shown in FIG. The fresh air charging chamber 40 is formed so as to surround three cylinders in the cylinder body 12. Three scavenging passages 48A, 48A, 48B are respectively formed around the cylinder bore 20, and these scavenging passages 48A, 48A, 48B are connected to the fresh air charging chamber 40 at the upstream end, and the cylinder sleeve 18 at the downstream end. Are connected to the combustion chamber 28 via main scavenging ports 44 and 44 and an auxiliary scavenging port 46 which are open to the inside. Each of these scavenging passages 48A, 48A, 48B is
0 are connected in parallel with each other.

In this embodiment, the two main scavenging ports 44, 44 are arranged at positions substantially opposite to each other, and are located between the two main scavenging ports 44, 44 on the opposite side of the exhaust port 50. Is provided with an auxiliary scavenging port 46. With these arrangements, so-called schneele scavenging is performed.

The fresh air supply passage 37 includes, from the upstream, an intake passage 38, a fresh air charging chamber 40, and scavenging passages 48A, 48A,
The scavenging pump 34 supplies fresh air to the combustion chamber 28.

In this embodiment, the cylinder body 1
2 around a fresh air filling chamber 40 provided in
2 is formed, and cooling water pumped from a water pump (not shown) is supplied to the water jacket 52 to cool the cylinder body 12. Thus, not only the cylinder sleeve 18 but also the fresh air in the fresh air filling chamber 40 that has been pressurized and heated by the scavenging pump 34 can be cooled, and the charging efficiency can be increased.

With the above configuration, fresh air pressurized by the scavenging pump 34 is charged from the intake passage 38 into the fresh air charging chamber 40. The fresh air filled in the fresh air charging chamber 40 passes through the scavenging passages 48A, 48A, 48B and the main scavenging ports 44, 4
4. Introduced from the auxiliary scavenging port 46 toward the combustion chamber 28.

The fresh air introduced into the combustion chamber 28 mixes with the fuel ejected from the injector 32 to become an air-fuel mixture and flows in the combustion chamber 28. This mixture is ignited by the spark plug 30 and explodes. The burned gas is then guided from the exhaust port 50 through the exhaust passage 51 to an exhaust expansion chamber (not shown), expands, and bosses (not shown) of the propeller 8.
From the sea. The fresh air filling chamber 40 is provided with an auxiliary injector 33. The auxiliary injector 33 plays a role of supplementarily supplementing the fuel when the discharge amount of the injector 32 becomes insufficient.

Fresh air is pumped from the scavenging pump 34 through a fresh air supply passage 37 composed of an intake passage 38, a fresh air filling chamber 40, and scavenging passages 48A, 48A, 48B. When the scavenging port 46 is opened by the piston 22 and communicates with the combustion chamber 28, it is introduced into the combustion chamber 28. Of the three cylinders, the main scavenging port 44 of any one of the cylinders,
44 or the auxiliary scavenging port 46 is not open, fresh air pumped from the scavenging pump 34 is supplied to the fresh air charging chamber 4.
At the same time that the main scavenging port 44, 44 or the auxiliary scavenging port 46 of the next cylinder is opened, the charged fresh air is introduced into the combustion chamber 28 of the next cylinder.

Next, another embodiment of the adjusting structure for matching the heights of the output pulley 72 and the input pulley 62 will be described with reference to FIG.

Although the structure is basically the same as that of FIG.
2 is being fixed to the input shaft 56. Therefore, the same reference numerals are given to other portions, and the description thereof will be omitted. This adjustment mechanism is performed by a shim 68 inserted between the input pulley 62 and the input shaft 56.
That is, after variously preparing and measuring the thickness of the shim 68,
This is performed by selecting a shim having the same height and inserting the selected shim 68 with the nut 58 and the input pulley 62 removed.

Next, another embodiment of an adjusting structure for matching the heights of the output pulley 72 and the input pulley 62 will be described with reference to FIG.

Although the structure is basically the same as that of FIG. 6, the difference is that there is no adjusting mechanism on the input pulley 62 side.
It is provided on the output pulley 72 side. The other parts have substantially the same structure, and therefore, are denoted by the same reference numerals, and description thereof will be omitted. A ring gear 74 is fixed to the flywheel magneto 11, and an output pulley 72 is fixed to the ring gear 74 by a bolt 76 via a shim 68 for height adjustment. This adjustment mechanism is performed by a shim 68 inserted between the output pulley 72 and the ring gear 74. That is, by preparing and measuring various thicknesses of the shim 68, selecting the shim having the same height, inserting the selected shim 68 with the bolt 76 and the output pulley 76 removed. Done.

In this embodiment, the scavenging pump 34
Are arranged substantially in front of the crankshaft 10. That is, the scavenging pump 34 is disposed in front of the crankcase 14. Therefore, even when the scavenging pump 34 is installed, the upward protrusion of the crankshaft 10 does not increase. Further, since the scavenging pump 34 having a relatively large volume is not installed on the side of the crankshaft 10, the width of the engine 7 is not increased. Therefore, even in the case where two outboard motors are installed on the hull, that is, in the case of a so-called two-board outboard motor, the outboard motors can be installed without interference on both sides. Further, since the relatively heavy scavenging pump 34 is installed close to the tilt pin 5, the force at the time of tilting up can be reduced.

In this embodiment, an in-line three-cylinder engine has been described. However, the present invention can be similarly applied to a V-type engine as long as both cylinders are arranged substantially rearward from the crankshaft 10. Needless to say.

[0029]

According to the present invention, the scavenging pump can be arranged close to the crankshaft. In addition, the upward protrusion associated with the arrangement of the scavenging pump is reduced, and the lateral protrusion of the crankshaft is also reduced. Therefore, the height of the engine is not increased, and the width of the engine is small, so that it is convenient to mount the engine on two engines or the like, and the arrangement is rational and compact for the outboard motor.

[Brief description of the drawings]

FIG. 1 is a side view of an entire outboard motor to which the present invention is applied.

FIG. 2 is a plan view of FIG.

FIG. 3 is a side view of an engine alone.

FIG. 4 is a sectional view taken along line IV-IV of FIG. 3;

5 is a cross-sectional view taken along line VV of FIG. 2, illustrating a drive mechanism of a scavenging pump and a height adjusting structure of a pulley.

FIG. 6 is a cross-sectional view corresponding to FIG. 5, showing another structure for adjusting the height of the pulley.

FIG. 7 is a sectional view corresponding to FIG. 5, showing another height adjusting structure of the pulley.

[Explanation of symbols]

 1 outboard motor 7 engine 10 crankshaft 12 cylinder body 14 crankcase 22 piston 28 Combustion chamber 32 Injector 34 Scavenging pump 36 Throttle valve 44 Main scavenging port 52 Belt 56 ··· Input shaft 62 ···· Input pulley 68 ····· Shim 72 ···· Output pulley

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F02B 33/36 F02B 33/44 F02B 67/00

Claims (1)

(57) [Claims] 1. A crankshaft is arranged substantially vertically, and a cylinder, in which a piston connected to the crankshaft reciprocates, is arranged rearward in a traveling direction, and is driven by the crankshaft. Formed in a cylinder
In the outboard motor for e emissions <br/> gin equipped with a supercharger to supply fresh air to the combustion chamber has the supercharger side by side above the front portion of the crank shaft is disposed, to the upper and the input shaft Protrude the crank
Connects to the upper end of the shaft and connects to the new combustion chamber.
Point the air supply passage inside the turbocharger to the side of the crankshaft
An engine for an outboard motor, wherein the engine is arranged in a vertical position .